fix: Envs from additional apks not override default values

[pawelpasterz]

Fixes #2111

Test Plan

How do we know the code works?

1. run ./gradlew flankFullRun
2. create config with

   additional-app-test-apks:
     - test: [...].apk
       environment-variables:
          someVariable: true
   

3. Your app from additional should see overridden variables

Checklist

• Unit tested

[pawelpasterz]

@flank-it

[github-actions]

Integration tests succeed for all OSs ✅
Windows Build scan:
MacOS Build scan: https://gradle.com/s/wkimh3jyubvnk
Linux Build scan: https://gradle.com/s/i2tjrzos2bedk
Workflow run https://github.com/Flank/flank/actions/runs/1104372435

[github-actions]

Timestamp: 2021-08-09 07:06:22
Buildscan url for ubuntu-workflow run 1111908716
https://gradle.com/s/qn5tfntnrcghu